1. The invention relates to a changing device for a lens holder of a connecting head for machining a workpiece by means of a laser beam.
2. Description of the Relevant Art
DE 295 07 189 U1 has already disclosed a connecting head for machining a workpiece by means of a laser beam. The laser beam is focused with the aid of a focusing optical system present in a connecting head. The laser beam emerges through a cutting nozzle after traversing the focusing optical system. In this case, the focusing optical system is fitted, such that it can be adjusted in the direction of and transverse to its optical axis, on a lens holder. The lens holder is a withdrawable part and can be inserted into a connecting head housing and withdrawn therefrom. In order to facilitate the machining of the workpiece by means of a laser beam, a process gas emerges under pressure together with the laser beam through the cutting nozzle fitted on the connecting head.
Such connecting heads are used, for example, in laser cutting installations. The laser cutting is extremely flexible by comparison with rival separating methods (punching, sawing, etc.). Changing to new cutting contours, materials or workpiece thicknesses can be performed in this case comparatively quickly and in an automated fashion. A plurality of machine parameters are frequently changed for this purpose, for example the contour program, the laser output, the feed rate, the type and pressure of the process gas, the distance between the connecting head and workpiece, and the focusing position. In addition to matching these parameters, it is, in particular, also frequently necessary to change the focal length of the focusing optical system, the nozzle diameter, the nozzle type etc., thus giving rise to the need to change the focusing optical system and the cutting nozzle.
Since the focusing optical system and the cutting nozzle are subject to wear in normal use, ensuring a high process quality requires regular inspection, possibly with subsequent exchange, or regular exchange of the focusing optical system and cutting nozzle. Both the workpiece to be machined and the laser cutting installation could be damaged by worn or damaged focusing optical systems or cutting nozzles.
In order to permit changing of the focusing optical system, it is known from German Patent Application DE 196 55 127 to integrate in the connecting head a changing device for focusing optical systems, in order to be able to arrange in the machining beam path focusing optical systems of different focal lengths at different distances from the cutting nozzle. The individual focusing optical systems are arranged in this case either on turntables or on slides which are situated in different planes perpendicular to the machining beam path.
JP 10-006 062 discloses a changing device for cutting nozzles of a laser machining head in which a plurality of cutting nozzles are accommodated in a magazine. So as to hold the cutting nozzles in the magazine, the latter has appropriate holes behind the edges of which a flange of the respective cutting nozzle engages in each case when the latter is inserted with a slight pressure. The cutting nozzle is held on the connecting head with the aid of appropriate locking means such that after a cutting nozzle has been set down in the magazine another cutting nozzle can be taken from the magazine with the aid of the connecting head.
In a further known changing device for cutting nozzles (U.S. Pat. No. 5,101,089), it is possible to exchange various cutting nozzle tips which can be held by a bayonet catch on the nozzle body of a connecting head or in a holding device of a magazine. For the purpose of changing the cutting nozzle tip, the latter is pushed into a corresponding holding space and firstly fastened in the holding device by rotating the connecting head such that further rotation releases the bayonet connection between the cutting nozzle tip and the connecting head or the nozzle body. The connecting head can then be withdrawn in order to take another cutting nozzle tip from the magazine by firstly rotating the connecting head to make the bayonet connection between the connecting head and cutting nozzle tip, and then releasing the bayonet connection between the cutting nozzle tip and holding device. When locking and unlocking the bayonet connections, it is also possible in this case to rotate the holding device by means of a motor instead of the connecting head.
The object of the invention is to provide a changing device which renders it possible to match the connecting head of a laser machining installation quickly and reliably to the particular machining task.
Thus, the invention provides that the changing device for a lens holder of a connecting head for machining a workpiece by means of a laser beam has at least two magazine stations, of which each has a holding device for gripping and holding a lens holder, and an actuating device for fastening means which are provided on the connecting head and fix the lens holder, a locking and unlocking device advantageously being provided as an actuating device.
This renders possible quick and automated changing of a focusing optical system arranged in a lens holder, without the need to undertake substantial changes for automation on the connecting head itself. Particularly when use is made of a connecting head which has a focusing optical system preadjusted in the direction of the optical axis and perpendicular thereto, and which is provided for manually changing the focusing optical system, automatic changing is possible with the aid of the changing device according to the invention without the need to undertake essential changes at the connecting head, since the changing device has all the means required for changing.
In order to achieve particularly flexible automation, it is possible when changing the focusing optical system simultaneously to undertake a change to the focal position and/or the focal length. However, in most cases this also requires simultaneous exchange of the cutting nozzle, since in some circumstances a change in the focal length and/or the focal position can drastically change the laser beam radius in the cutting nozzle region, or the beam caustic. If the cutting nozzle and the laser beam caustic are not coordinated with one another, there can be a severe worsening of the machining quality. In the worst case, the cutting nozzle can burn up and the workpiece to be machined can be damaged.
In order to take precautions here, it is possible for the nozzle opening generally to be selected to be so large that the machining beam always passes acceptably through the nozzle opening independently of the focusing optical systems used. However, this increases the gas consumption and, moreover, does not achieve the optimum possible machining result in many cases.
In order to provide a remedy here, it is possible in principle to provide on the changing device according to the invention further magazine stations at which cutting nozzles can be changed automatically. However, in order to carry out automatic changing of the focusing optical system and another function element of the connecting head, particularly the cutting nozzle, particularly quickly, it is provided in the case of an advantageous embodiment of the invention that provided at each magazine station are a further holding device for gripping and holding a further function element and a further actuating device for fastening means which fix the further function element on the connecting head, with the result that the lens holder and the further function element at the same magazine station can be removed from the connecting head or fitted thereon, the further holding device being constructed, in particular, for gripping and holding a cutting nozzle.
The invention thus renders it possible to change two function elements of a connecting head for a laser machining installation at a single magazine station of a changing device. The connecting head therefore need only be moved to a first empty magazine station, where the function elements to be changed, that is to say the lens holder and the cutting nozzle, are gripped by the changing device and detached from the connecting head. The connecting head is then moved to another magazine station where the desired mutually coordinated function elements, that is to say the lens holder with the focusing optical system required for further machining, and the cutting nozzle coordinated therewith are mounted. The insertion of the required focusing optical system and the fitting of the cutting nozzle are performed there.
Thus, the construction, according to the invention, of the magazine stations of the changing device renders it possible to change the focusing optical system and the associated cutting nozzle in an automated fashion at a single magazine station, resulting thereby in a space-saving design of the changing device and in simple control of the changing operation.
In an expedient development of the invention, it is provided that provided for gripping and holding the cutting nozzle is a gripper which acts on the outer circumference of the latter and can be rotated about an axis of rotation coaxial with the axis of a gripped cutting nozzle, in order to detach a gripped cutting nozzle from the connecting head, or fasten it on the latter.
It is particularly expedient when the gripper is constructed as a screw-in and screw-out device.
Since the individual function elements and, in particular, the focusing optical system are subject to wear and/or can be damaged during the machining of workpieces, it is particularly expedient for each magazine station to be assigned a monitoring device in order to check the state of a function element, in particular the focusing optical system, removed from a connecting head. It is particularly expedient in this case for the monitoring device to be an optical sensor which supplies an outward signal from which the state and/or the position of the monitored function element can be derived.
It is possible with the aid of the monitoring device provided on the changing device according to the invention to establish whether a function element is still in an acceptable state after use in the laser cutting installation, in order to be held ready for further use, or whether it must be repaired or replaced. In particular, it is possible to use an optical sensor to detect the presence or absence of a focusing optical system, and/or the degree of contamination thereof and/or its focal position. In particular, it can be established in monitoring or detecting the state of a cutting nozzle whether the nozzle opening is still round.
In order to lengthen the service life of function elements of a connecting head which become contaminated while being used in a laser cutting installation, and to improve their readiness for use, it is provided in an expedient development of the invention that a cleaning device for a function element, in particular a brush device for cleaning cutting nozzles, is arranged at each magazine station.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.